System Level Thermal Evaluation and Optimization of an Automotive Module Incorporating Several Power Packages

2005 ◽  
Author(s):  
Victor Chiriac ◽  
Tom Lee ◽  
Kim Gauen
Keyword(s):  
Ambient Temperature ◽  
Thermal Performance ◽  
Heat Dissipation ◽  
Daily Basis ◽  
System Level ◽  
Main Concern ◽  
Transfer Coefficients ◽  
Passive Components ◽  
Reference Design ◽  
System Module

The conjugate thermal performance of a microelectronics module incorporating several power packages and additional passive components in a custom environment is evaluated and further optimized using numerical simulation and experimental validation. The automotive industry deals on a daily basis with various package and module-level thermal issues when managing the routing of very high current. The study provides a better understanding of the strengths and weaknesses of the IC packaging incorporation into a system module level, for both present and future product development. The reference design is evaluated at a system level, and several improvements are identified to enhance the overall thermal performance. The main concern is the possibility of exceeding the thermal budget for the large system incorporating seven power packages with additional sources of heat dissipation in an enclosure, at an external ambient temperature of 85°C. The overall thermal impact of the metal trace dissipation, header heating and other passive components under various powered conditions is evaluated. An additional revised model includes additional passive components (32 LD SOIC and QFN packages) on the PCB, a modified harness extending ∼ 30.4 cm outside the enclosure, and additional heating in the connectors. Several additional cases are investigated, varying the heat transfer coefficients outside the enclosure, at an ambient temperature of 85°C. The peak temperatures range from 121.4°C to 126.4°C and the corresponding junction-to-ambient thermal resistances (Rja) vary from 11.03°C/W to 12.5°C/W. The optimized numerical model approximates closely the empirical results (121–126°C vs. 127.5°C), within 1–2%.

System Level Thermal Optimization of an Automotive Lightning Module Incorporating Several Power Devices

2007 ◽  
Author(s):  
Victor Chiriac ◽  
Tien-Yu Tom Lee
Keyword(s):  
Thermal Performance ◽  
Power Dissipation ◽  
Heat Dissipation ◽  
System Level ◽  
Total Power ◽  
Main Concern ◽  
Optimized Design ◽  
Passive Components ◽  
Thermal Budget ◽  
The Impact

The conjugate thermal performance of microelectronics module incorporating several power packages and additional passive components in a custom environment is evaluated and further optimized using numerical simulation and experimental validation. The automotive industry deals on a daily basis with multiple packaging and module-level thermal issues when reducing the size of components for a lightning system in a car, while managing the routing of very high current. The study provides a better understanding of the strengths and weaknesses of the IC incorporation into a system module level, for both present and future product development. The reference design is evaluated at a system level, and several improvements are identified to enhance the overall thermal performance of the lightning system. The main concern is related to the possibility of exceeding the thermal budget for a large system incorporating several PQFN (Power Quad Flat No-Lead Package) packages with additional heat dissipation devices in an enclosure, at an external ambient temperature of 85°C. Due to the compactness of the device, there are only limited solutions to extract the heat from the high power dissipation system. The impact on the thermal balance of the trace dissipation, the location and size of the pins connecting the two boards (motherboard and daughter board) forming the system, the header heating and other passive components under various powered conditions are evaluated. A revised model includes additional pins (reduced diameter), modified motherboard and harness structures and their locations; the impact of additional heater traces on both top and bottom surfaces of the motherboard, and a modified daughter board design, is also evaluated. The resulting peak temperatures range from 118.3°C to 137.3°C and the corresponding junction-to-ambient thermal resistances (Rja) vary from 8.4°C/W to 8.8°C/W. Rja is defined as the temperature difference between the peak device and ambient divided by the total power dissipation of the PQFN packages. An optimized design is further evaluated, with lowered thermal resistance from the motherboard, the board-to-board pins, the junction box board, and the wiring harness. The thermal budget is satisfied, as the peak temperatures reached by the two designs are below the 150°C limit. Additional experimental results are used to benchmark the simulation results, within 1–6% accuracy.

System-Level Transient Thermal Analysis for Performance Optimization of High Power Microelectronics

2003 ◽  
Author(s):  
Victor Adrian Chiriac ◽  
Tien-Yu Tom Lee ◽  
H. S. Chen
Keyword(s):  
Thermal Performance ◽  
Performance Optimization ◽  
Numerical Study ◽  
Optimal Operation ◽  
System Level ◽  
Main Concern ◽  
Efficient Operation ◽  
Normal Test ◽  
Transient Thermal ◽  
Short Time

The increasing trend in power levels and densities leads to the need of design thermal optimization, at either module or system level. A numerical study using finite-volume software was conducted to model the transient thermal behavior of a system including a package dissipating large amounts of power over short time durations. The system is evaluated by choosing the appropriate heat sink for the efficient operation of the device under 100W of constant powering, also to enhance the thermal performance of the enclosure/box containing the test stack-up. The intent of the study is to provide a meaningful understanding and prediction of the high transient powering scenarios. The study focuses on several powering and system design scenarios, identifying the main issues encountered during a normal device operation. The power source dissipates 100W for 2 seconds then is cooled for another 2 seconds. This thermal cycle is likely to occur several times during a normal test-up, and it is the main concern of the manufacturers not to exceed a limit temperature during the device testing operation. The transient trend is further extrapolated analytically to extract the steady state peak temperature values, in order to maintain the device peak temperatures below 120°C. The benefit of the study is related to the possibility to extract the maximum/minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range, for the optimal operation of the device. The flow and heat transfer fields are thoroughly investigated. By using a combination of numerical and analytical study, the thermal performance of the device undergoing infinity of periodic thermal cycles is further predicted.

scholarly journals Flooded Two-Phase Flow Dynamics and Heat Transfer With Engineered Wettability on Microstructured Surfaces

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Bo Chen ◽  
Zhou Zhou ◽  
Junxiang Shi ◽  
Steven R. Schafer ◽  
Chung-Lung (C. L.) Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Dissipation ◽  
Upward Movement ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Vof Model ◽  
Pulling Forces ◽  
3D Volume ◽  
Hydrophobic Material

Due to excessive droplet feeding, a period of flooding occurs as part of a typical droplet based thermal management cycle. The conventional superhydrophilic surface, which is designed for thin film evaporation because of its highly wettable character, has a limited improvement on the thermal performance during the flooded condition. This paper investigates microstructures which combine micropillars and four engineered wettability patterns to improve the heat dissipation rate during flooding. Using the transient, 3D volume-of-fluid (VOF) model, the bubble behaviors of growth, coalescence, and departure are analyzed within different microstructures and the effects of pillar height and wettability patterns on the thermal performance are discussed. The wettability gradient patched on the pillar's side is demonstrated to promote the bubble's upward movement due to the contact angle difference between the upper and lower interfaces. However, insufficient pulling force results in large bubbles being pinned at the pillar tops, which forms a vapor blanket, and consequently decreases the heat transfer coefficient. When only a patch of hydrophobic material is present on the pillar top, effective pulling forces can be developed to help bubbles in the lower level depart from the pillar forest, since bubble merging between them generates most of the power required to pull the bubbles to the surface. The simulation results, including heat source temperatures and heat transfer coefficients, indicate that a patch of hydrophobic material on the pillar top works best out of all of the cases studied.

Thermal Management for High Power Light-Emitting Diode Street Lamp

2010 ◽  
Author(s):  
M. Ying ◽  
S. M. L. Nai ◽  
P. Shi ◽  
J. Wei ◽  
C. K. Cheng ◽  
...  
Keyword(s):  
Thermal Management ◽  
Thermal Performance ◽  
High Power ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
System Level ◽  
Light Emitting ◽  
High Power Led ◽  
Street Lamp ◽  
Lamp System

Light-emitting diode (LED) street lamp has gained its acceptance rapidly in the lighting system as one of choices for low power consumption, high reliability, dimmability, high operation hours, and good color rendering applications. However, as the LED chip temperature strongly affects the optical extraction and the reliability of the LED lamps, LED street lamp performance is heavily relied on a successful thermal management, especially when applications require LED street lamp to operate at high power and hash environment to obtain the desired brightness. As such, a well-designed thermal management, which can lower the LED chip operation temperature, becomes one of the necessities when developing LED street lamp system. The current study developed an effective heat dissipation method for the high power LED street lamp with the consideration of design for manufacturability. Different manufacturable structure designs were proposed for the high power street lamp. The thermal contact conductance between aluminum interfaces was measured in order to provide the system assembly guidelines. The module level thermal performance was also investigated with thermocouples. In addition, finite element (FE) models were established for the temperature simulation of both the module and lamp system. The coefficient of natural convection of the heat sink surface was determined by the correlation of the measurement and simulation results. The system level FE model was employed to optimize and verify the heat dissipation concepts numerically. An optimized structure design and prototype has shown that the high power LED street lamp system can meet the thermal performance requirements.

Steady-State and Transient Thermal Performance Optimization of Power Automotive Modules

2009 ◽  
Author(s):  
Victor Chiriac
Keyword(s):  
Steady State ◽  
Thermal Performance ◽  
Numerical Study ◽  
Peak Temperature ◽  
System Level ◽  
Main Concern ◽  
Thermal Impact ◽  
Automotive Applications ◽  
Isothermal Boundary ◽  
Transient Thermal

An extensive 3-D conjugate numerical study is conducted to assess the thermal performance of power packages for automotive applications. The automotive industry deals on a daily basis with various package and module-level thermal issues when managing the routing of very high current. The study provides a better understanding of the strengths and weaknesses of IC incorporation into a system module, for present and future product development. Several packages are investigated, ranging from smaller die/flag size to larger ones, single or multiple heat sources, operating under various powering and boundary conditions. The steady state and transient thermal impact of the thicker lead frame and die attach material on the overall thermal behavior is evaluated. The main concern is exceeding the thermal budget at an external ambient temperature of 85°C, specific for the relatively extreme automotive operating environments. Under one steady state (1W) operating scenario, the PQFN package reaches a peak temperature of ∼106.3°C, while under 37W@40ms of transient powering, the peak temperature reached by the corner FET is ∼260.8°C. With an isothermal boundary (85°C) attached to the board backside, the junction temperature does not change, as the PCB has no significant thermal impact. When the isothermal boundary is attached to package bottom, peak temperature drops by 20% after 40 ms. Additional system level with multiple optimized packages placed on a custom PCB is evaluated numerically and experimentally, placing an emphasis on the superior thermal performance of this new class of power packages for automotive applications. The optimized numerical model approximates closely the empirical results (121–126°C vs. 127.5°C), within 1–2%.

scholarly journals Internal Coating of Ureteral Stents with Chemical Vapor Deposition of Parylene

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 739
Author(s):  
Sara Felicitas Bröskamp ◽  
Gerhard Franz ◽  
Dieter Jocham
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Silver Ions ◽  
Daily Basis ◽  
Second Step ◽  
Silver Layer ◽  
Main Concern ◽  
Ureteral Stents ◽  
Balloon Catheters

Ureteral balloon catheters and ureteral stents are implanted in large quantities on a daily basis. They are the suspected cause for about a quarter of all the nosocomial infections, which lead to approx. 20,000 deaths in Germany alone. To fight these infections, catheters should be made antibacterial. A technique for an antibacterial coating of catheters exhibiting an aspect ratio of up to 200 consists of a thin silver layer, which is deposited out of an aqueous solution, which is followed by a second step: chemical vapor deposition (CVD) of an organic polymeric film, which moderates the release rate of silver ions. The main concern of the second step is the longitudinal evenness of the film. For tubes with one opening as balloon catheters, this issue can be solved by applying a descendent temperature gradient from the opening to the end of the catheter. An alternative procedure can be applied to commercially available ureteral stents, which exhibit small drainage openings in their middle. The same CVD as before leads to a longitudinal homogeneity of about ±10%—at very low costs. This deposition can be modeled using viscous flow.

scholarly journals Influence of Ambient Temperature on Radiative and Convective Heat Dissipation Ratio in Polymer Heat Sinks

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2286
Author(s):  
Jan Kominek ◽  
Martin Zachar ◽  
Michal Guzej ◽  
Erik Bartuli ◽  
Petr Kotrbacek
Keyword(s):  
Heat Transfer ◽  
Ambient Temperature ◽  
Convective Heat ◽  
Heat Dissipation ◽  
High Surface ◽  
Heat Sinks ◽  
Fourth Power ◽  
Molding Process ◽  
Ambient Temperatures ◽  
University Of Technology

Miniaturization of electronic devices leads to new heat dissipation challenges and traditional cooling methods need to be replaced by new better ones. Polymer heat sinks may, thanks to their unique properties, replace standardly used heat sink materials in certain applications, especially in applications with high ambient temperature. Polymers natively dispose of high surface emissivity in comparison with glossy metals. This high emissivity allows a larger amount of heat to be dissipated to the ambient with the fourth power of its absolute surface temperature. This paper shows the change in radiative and convective heat transfer from polymer heat sinks used in different ambient temperatures. Furthermore, the observed polymer heat sinks have differently oriented graphite filler caused by their molding process differences, therefore their thermal conductivity anisotropies and overall cooling efficiencies also differ. Furthermore, it is also shown that a high radiative heat transfer leads to minimizing these cooling efficiency differences between these polymer heat sinks of the same geometry. The measurements were conducted at HEATLAB, Brno University of Technology.

scholarly journals TEG Design for Waste Heat Recovery at an Aviation Jet Engine Nozzle

2018 ◽  
Vol 8 (12) ◽  
pp. 2637 ◽  
Author(s):  
Pawel Ziolkowski ◽  
Knud Zabrocki ◽  
Eckhard Müller
Keyword(s):  
Fuel Consumption ◽  
Power Output ◽  
Waste Heat ◽  
Positive Impact ◽  
Element Model ◽  
System Level ◽  
Specific Power ◽  
Transfer Coefficients ◽  
Te Modules ◽  
Te Material

Finite element model (FEM)-based simulations are conducted for the application of a thermoelectric generator (TEG) between the hot core stream and the cool bypass flow at the nozzle of an aviation turbofan engine. This work reports the resulting requirements on the TEG design with respect to applied thermoelectric (TE) element lengths and filling factors (F) of the TE modules in order to achieve a positive effect on the specific fuel consumption. Assuming a virtual optimized TE material and varying the convective heat transfer coefficients (HTC) between the nozzle surfaces and the gas flows, this work reports the achievable power output. System-level requirement on the gravimetric power density (>100 Wkg−1) can only be met for F ≤ 21%. When extrapolating TEG coverage to the full nozzle surface, the power output reaches 1.65 kW per engine. The assessment of further potential for power generation is demonstrated by a parametric study on F, convective HTC, and materials performance. This study confirms a feasible design range for TEG installation on the aircraft nozzle with a positive impact on the fuel consumption. This application translates into a reduction of operational costs, allowing for an economically efficient TEG-installation with respect to the cost-specific power output of modern thermoelectric materials.

Ambient Temperature as a Strong Zeitgeber of Circadian Rhythms in Response to Temperature Sensitivity and Poor Heat Dissipation Abilities in Subterranean African Mole-Rats

2021 ◽  
pp. 074873042110342
Author(s):  
Daniel W. Hart ◽  
Barry van Jaarsveld ◽  
Kiara G. Lasch ◽  
Kerryn L. Grenfell ◽  
Maria K. Oosthuizen ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Ambient Temperature ◽  
Heat Dissipation ◽  
Direct Consequence ◽  
Ecological Constraints ◽  
Photic Entrainment ◽  
Mole Rat ◽  
Intimate Link ◽  
Response To Temperature ◽  
First Time

Mammals have evolved circadian rhythms in internal biological processes and behaviors, such as locomotor activity (LA), to synchronize to the environmental conditions they experience. Photic entrainment of LA has been well established; however, non-photic entrainment, such as ambient temperature ( Ta), has received much less attention. To address this dearth of knowledge, we exposed two subterranean endothermic-homeothermic African mole-rat species, the solitary Cape mole-rat ( Georychus capensis [GC]) and social Mahali mole-rat ( Cryptomys hottentotus mahali [CHM]), to varying Ta cycles in the absence of light. We showed that the LA rhythms of these two species entrain to Ta cycles and that the majority of LA occurred during the coolest 12-h period. LA confined to the coolest Ta periods may be the direct consequence of the poor heat dissipation abilities of African mole-rats brought about by physiological and ecological constraints. Recently, it has been hypothesized that Ta is only a strong zeitgeber for circadian rhythms in species whose thermoregulatory abilities are sensitive to changes in Ta (i.e., heterotherms and ectotherms), which previously has excluded endothermic-homeothermic mammals. However, this study demonstrates that Ta is a strong zeitgeber or entrainer for circadian rhythms of LA in subterranean endothermic-homeothermic mammals as a consequence of their sensitivity to changes in Ta brought about by their poor heat dissipation abilities. This study reinforces the intimate link between circadian rhythms and thermoregulation and conclusively, for the first time, provides evidence that Ta is a strong zeitgeber for endothermic-homeothermic mammals.

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